protected TypeToken() {
    this.runtimeType = capture();
    checkState(
        !(runtimeType instanceof TypeVariable),
        "Cannot construct a TypeToken for a type variable.\n"
            + "You probably meant to call new TypeToken<%s>(getClass()) "
            + "that can resolve the type variable for you.\n"
            + "If you do need to create a TypeToken of a type variable, "
            + "please use TypeToken.of() instead.",